The use of solid block detergents in institutional and industrial cleaning operations was pioneered in technology claimed in the Fernholz et al. U.S. Reissue Pat. Nos. 32,763 and 32,818. Further, pelletized materials are shown in Gladfelter et al., U.S. Pat. Nos. 5,078,301, 5,198,198 and 5,234,615. Extruded materials are disclosed in Gladfelter et al., U.S. Pat. No. 5,316,688. The solid block format is a safe, convenient and efficient product format. In the pioneering technology, substantial attention was focused on how the highly alkaline material, based on a substantial proportion of sodium hydroxide, was cast and solidified. Initial solid block products (and predecessor powder products) used a substantial proportion of a solidifying agent, sodium hydroxide hydrate, to solidify the cast material in a freezing process using the low melting point of sodium hydroxide monohydrate (about 50.degree. C.-65.degree. C.). The active components of the detergent were mixed with the molten sodium hydroxide and cooled to solidify. The resulting solid was a matrix of hydrated solid sodium hydroxide with the detergent ingredients dissolved or suspended in the hydrated matrix. In this prior art cast solid and other prior art hydrated solids, the hydrated chemicals are reacted with water and the hydration reaction is run to substantial completion. The sodium hydroxide also provided substantial cleaning in warewashing systems and in other use loci that require rapid and complete soil removal. In these early products sodium hydroxide was an ideal candidate because of the highly alkaline nature of the caustic material provided excellent cleaning. Another sodium hydroxide and sodium carbonate cast solid process using substantially hydrated sodium materials was disclosed in Heile et al. U.S. Pat. Nos. 4,595,520 and 4,680,134.
Similarly, pioneering technology relating to the use of solid pelleted alkaline detergent compositions in the form of a water soluble bag assembly and an extruded alkaline solid material wrapped in a water soluble film has also been pioneered by Ecolab Inc. These products within the water soluble bag can be directly inserted into a spray on dispenser wherein water dissolves the bag and contacts the soluble pellet or extruded solid, dissolves the effective detergent ingredients, creates an effective washing solution which is directed to a use locus.
In recent years, attention has been directed to producing a highly effective detergent material from less caustic materials such as soda ash, also known as sodium carbonate, because of manufacturing, processing, etc. advantages. Sodium carbonate is a mild base, and is substantially less strong (has a smaller K.sub.b) than sodium hydroxide. Further on an equivalent molar basis, the pH of the sodium carbonate solution is one unit less than an equivalent solution of sodium hydroxide (an order of magnitude reduction in strength of alkalinity). Sodium carbonate formulations were not given serious consideration in the industry for use in heavy duty cleaning operations because of this difference in alkalinity. The industry believed carbonate could not adequately clean under the demanding conditions of time, soil load and type and temperature found in the institutional and industrial cleaning market. A few sodium carbonate based formulations have been manufactured and sold in areas where cleaning efficiency is not paramount. Further solid detergents made of substantially hydrated, the carbonate content contained at least about seven moles of water of hydration per mole of sodium carbonate were not dimensionally stable. The substantially hydrated block detergent tended to swell and crack upon aging. This swelling and cracking was attributed to changing of the sodium carbonate hydration states within the block. Lastly, molten hydrate processing can cause stability problems in manufacturing the materials. Certain materials at high melting temperatures in the presence of water can decompose or revert to less active or inactive materials. The carbonate detergents could under certain circumstances corrode metal surfaces. Ware made of active metals such as aluminum are subject to such corrosion when carbonates are used as the alkalinity source.
Accordingly, a substantial need for mechanically stable solid carbonate detergent products, having equivalent cleaning performance without substantial metal corrosion, when compared to caustic based detergents, has arisen. Further, a substantial need has arisen for successful non-molten processes for manufacturing sodium carbonate based detergents that form a solid with minimal amounts of water of hydration associated with the sodium base. These products and processes must combine ingredients and successfully produce a stable solid product that can be packaged, stored, distributed and used in a variety of use locations.